Federal and state governments have imposed increasingly strict regulations over the years governing the levels of hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOx) pollutants that a motor vehicle may emit to the atmosphere.
One approach to reducing the emissions of these pollutants involves the use of a catalytic converter. The catalytic converter is placed within the exhaust gas stream between the exhaust manifold of the engine and the muffler of a vehicle.
A large percentage of a vehicles total cold start HC emissions occur during the time period while the catalytic converter is warming-up to operating temperature.
Several attempts have been made to reduce cold start emissions. For example: the catalytic converter has been moved as close to the engine as possible. In cases where the entire converter could not be moved close enough to the engine, a smaller warm-up converter is often used ahead of a second under-floor converter. In addition, catalytic converter improvements such as improved catalysts, and high-cell-density ceramic substrates with very thin walls that require less heat energy to reach operating temperature have been employed to reduce cold start emissions.
None of the above-mentioned approaches involves a fuel injector. Thus, there is a need to improve a fuel injector to more efficiently control the ignition and combustion properties during cold start-up to promote rapid catalyst warm-up.